D3.36 - Contact allergy to sodium metabisulfite in Singapore: A single-center retrospective study of patch test data from 2004 to 2021

Sulfites have been increasingly recognized as a cause of contact allergy in recent years, with multiple sources of exposure identified. The studied prevalence of sodium metabisulfite ranges from 1.9% to 3.8%. 

We aim to identify the frequency and relevance of contact allergy to sodium metabisulfite among patients undergoing patch testing at the National Skin Centre, Singapore.

We retrospectively analyzed patch test results of all patients who underwent patch testing with sodium metabisulfite from 2004 to 2021. Readings were performed on days 3 and 7. Descriptive analysis was performed for all variables.

468 patients were included, with a mean (SD) age of 41.6 (17.1) years. 165 (35.3%) were male. The commonest sites affected were the hands (99, 21.2%), face (92, 19.7%) and fingers (79, 16.9%). 118 (25.2%) had a history of atopic dermatitis.

21 (4.5%) had contact allergy to sodium metabisulfite, of which 3 (14.3%) showed a late positive reaction. The mean (SD) age was 45.2 (12.5) years, with 4 (19.0%) having a history of atopic dermatitis. 12 (57.1%) were male. The commonest sites affected were the hands (5, 23.8%), fingers (3, 14.3%) and back (3, 14.3%). Reactions were of exposed relevance in 1 (4.8%), unknown in 6 (28.6%), and not recorded in the remaining 14 (66.7%).

The prevalence of sodium metabisulfite contact allergy in our population exceeds those of other studied populations. However, none were deemed relevant. The limitations of this study include the large number of cases with undocumented relevance, and potential under-recognition of sources of sulfites by clinicians.